High temperature nickel base alloy



p 1960 v J. T. BROWN 2,951,757

HIGH TEMPERATURE NICKEL BASE ALLOY Filed March 7, 1958 ZSheetS-Sheet l o -9 mmm r r I I0 bf 03 0 bk: 2': 15 o o' o' o 0' g z z z z z 5 a- Q.-

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m 75 m H G) U. P z, :r o E o 9 MI 1. 1 L llllll I I I t o o a 8 8 o o o. 2- 2- 8 8 ysd-ssa1 WITNESSES- INVENTOR Jock T. Brown BY WTTORKEY Sept. 6, 1960 J. T. BROWN 2,951,757

HIGH TEMPERATURE NICKEL BASE ALLOY Filed March 7, 1958 2 Sheets-Sheet 2 Creep Tests Heat l8|7 7- E 5- |800F, 25,000 psi 0 2 5 8 o 3- I700F 30,000psi o I I l I l I l I I I I l 0 80 I60 240 320 400 480 Time (Hours) Fig.2.

I00: 0 Heat No I755 I Heat No. I778 A Heat No. I779 0 Heat No; I794 0 Heat No. I795 O. o 8 20. i E. (5 A= 100 Hours |Q B =5OO Hours |500F I600F |700F I800F 900F 2000F 3 A B'lABlABlLAJ'BlA BlAl B} 0 I I I I l l I 46 5O 54 58 62 66 70 x Fig.3.

United States Patent Ofiice 2,951,757 Patented Sept. 6, 1960 HIGH TEMPERATURE NICKEL BASE ALLOY Jack T. Brown, Monroeville, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 7, 1958, Ser. No. 719,886

6 Claims. (Cl. 75-171) This invention relates to nickel base alloys particularly suitable for use at extremely high temperatures.

There is a considerable need for an alloy that can be cast into members which may be employed at temperatures of from 1700 F. to 1800 F. and higher. Such alloys can be employed with advantage for the turbine blades of jet engines and gas turbines. Alloys that can withstand temperatures of 1800" F. to 1900 F. are desirable for use in creep testing machines which are ernployed in determining the properties of other known high temperature alloys being manufactured at the present time.

The requirements for such alloy compositions com prise the following:

(1) The alloys should be castable by precision casting techniques into sound members which conform to close tolerances;

(2) The alloys should be resistant to oxidation when exposed to the air at elevated temperatures of up to 1800" F.;

(3) The alloys should have good stress-rupture strength properties and a ductility of at least 3% along with abil ity to sustain stresses of well over 15,000 p.s.i. at temperatures of 1800 F. for periods of time of from 100 to 500 hours;

"(4) The alloys should have good room temperature tensile strength with a substantial ductility; and

(5) The alloys should have a high modulus of elasticity over the range of temperatures of use.

Other characteristics desirable in such high temperature alloys will be detailed hereinafter.

The object of the present invention is to provide an alloy suitable for casting members with substantial accuracy, the alloy having stress-rupture properties so that at temperatures of up to 1800 F. and higher the alloys will not fail in less than 100 hours at loads of in excess of 15,000 psi. with an elongation of atleast 3%.

A further object of the invention is to provide a nickel base casting alloy comprising predetermined critical proportions of cobalt, chromium, boron and zirconium along with controlled amounts of titanium, aluminum, tungsten and carbon as hardening components.

Other objects of the invention will in part be obvious and willin part appear hereinafter. For a better understanding of the nature and objects of the invention, reference should be had to the following detailed description and drawing, in which:

Figure 1 is a stress-rupture graph of the alloy's of the present invention;

Fig. 2 is a creep curve of several alloy specimens; and

Fig. 3 'is a curve plotting the stress against the timetemperature parameter for the alloys of the present invention.

An alloy composition which possesses the properties tabulated herein has been produced by melting under vacuum components to produce the following alloy composition in which all parts are by weight;

Broad Range, Preferred percent Range, percent Cobalt 9 to 11 9.5 to 10.5. Chromium 9 to 15 11 13. Tungsten 6 to in 7.5 to 8.5. Titanium 3.5 to 5.. 4.0 to 4.8. Aluminum 3 to 5.-.. 3.5 to 4.8. Carbon 0.04 to 0. 0.08 to 0.13. Boron 0.02 to 0. 0.04 to .08. Zirconium 0.01 to 0.2 0.02 to .08. Nickel Balance Balance.

In these alloys the titanium, aluminum, tungsten and carbon cooperate to provide a desired hardness and high temperature strength properties. The proportions of tungsten in this alloy are highly critical. The tungsten in the indicated proportions of from 6% to 10%, functions as a high temperature solid solution strengthening component.

The indicated small amounts of boron and zirconium have proven to be necessary to secure the good properties of the alloy and particularly a high ductility.

The oxygen and nitrogen content of the alloys should not exceed 0.01%, respectively. The alloys may comprise small amounts of ironordinarily not exceeding approximately 2%. Small amounts of sulfur and phos phorus not over 0.01% each may be present. Manganese and silicon in amounts of up to 0.5% may be present. The presence of incidental impurities and other minor additions, for example, molybdenum, vanadium and colurnbium should not exceed a total of approximately 3% by weight.

The alloys arepreferably Vacuum melted under a vacuum of the order of 10 microns or less absolute pressure. Vacuum casting of the melt has given excellent results. Casting of the melted alloy under an inert gas, such as argon also produces good cast members. However, melts of the alloy cast in air in precision casting molds have shown good results though greater variability of properties occur. Therefore, for best results the melted alloy should be protected from the air during melting and casting. The melting may be carried out in a vacuum induction furnace or in a vacuum arc melting furnace, either of the consumable are or non-consumable arc type.

The following examples illustrate the preparation of the alloy of the present invention:

EXAMPLE I In a vacuum induction furnace there was melted a charge which had the following analysis after casting:

Nickel 63.2 Chromium 10.5 Cobalt 9.83 Tungsten 7.76 Titanium 4.06 Aluminum 3.69 Boron .052 Zirconium .02 Carbon .098 Iron .17

Table I Heat B Zr Co Cr W Ti Al Fe Ni EXAMPLE IIII An alloy composition in accordance with the present invention was vacuum melted and permitted to solidify. The resulting solid mass of alloy was then remelted in an Room temperature tensile tests and several conventional short time tensile tests at the indicated elevated temperatures were conducted on the six alloys set forth in Examples I to III and in Table IH with the results as set forth in the following Table IV:

Table IV TENSILE RESULTS Test 0.2% Yield Ultimate Percent Percent Heat No Temp. Str. (p.s.i.) Str. (p.s.i.) Eiong. Bed. of

C F.) (1") Area R.T. 109,000 137. 000 8. 4 11. 5 R.T. 114,000 119,000 5. 3 7. 8 1. 800 53,000 69, 000 6. 3 9. 3 RT. 115, 000 121,000 4. 2 9. 4 1, 800 49,000 66, 000 3.1 1. 6 R.T. 118, 000 129,000 3. 6 8.5 R.T. 118,000 139, 000 7. 8 7. 9

The stress-rupture properties of the above five alloy compositions are set forth in the following Table V:

Table V STRESS-RUPTURE TEST RESULTS Initial Final Temp. Stress Rupture Rupture Hard- Gage Heat No. F.) (p.s.i.) Time Elong. ness, Hard- Comments (Hm) (percent) RC" ness,

RIIOII 1, 700 37, 500 17. 5 7. 9 34/36 34/36 1, 700 30, 000 91. 7 7. 8 35/37 36/38 1, 800 25, 000 21. 7 13. 4 34/36 33/35 1, 800 15, 000 293.0 14. 6 36/38 31/33 1, 800 12, 000 764.0 34/36 /32 Failed due to over, loading of machine after time indicated. 1, 800 30,000 13. 9 4. 2 35/36 36/38 800 25, 000 64. 6 4. 5 34/36 34/35 1, 800 000 139. 2 6. 4 35/36 35/36 1, 700 40, 000 14. 7 4. 2 38/39 37/39 1, 700 30, 000 219. 6 3. 7 36/37 35/36 500 000 48. 2 2. 8 37/38 38/39 1, 800 000 17. 2 3. 7 36/38 34/35 1, 800 20. 000 242. 9 3. 6 36/37 34/35 1, 700 40, 000 12. 1 4. 3 37 38 38/39 1, 700 30, 000 62. 8 2. 5 32/34 32/34 1, 900 10, 000 247. 7 6. 3 38/39 35/37 1, 800 25, 000 55. 6 4. 4 38/39 36/37 1, 700 30, 000 140. 4 3. 6 38/39 34/35 1, 800 25, 000 6. 6 3. 4 37/39 39/41 Defect at fracture. 1, 800 20, 000 300. 0 6.4 36/37 36/38 2, 000 10, 000 40. 6 9. 0 36/37 36/38 open air induction furnace and cast in air. The alloy is identified hereinafter as Heat No. 1795, and its analysis was as follows:

Table II Heat 0 B Zr Co Cr W Ti Al Fe Ni A number of other alloy compositions in accordance with the present invention were vacuum melted and vacuum cast. The heat numbers and the composition of the The following three heats of the alloys of this invention were melted under the conditions indicated and cast into members; the analyzed compositions are given for each:

Heat No. Melted Poured O B Zr Fe Cr 00 W Al T1 Ni 1X14 Vac 0.071 .08 11.9 10. 0 7. 66 4. 41 4. 25 61. 2 1817 Vac and Argon" .043 12 12 11.9 10. 0 7. 78 4. 36 4. 62 61. 4 1819 Argon 056 .05 26 12. 0 10. 0 7. 68 4. 29 4. 12 61. 1

resulting castings are set forth in the following Table III:

Room temperature tests of samples of each alloy are set forth in Table VI:

Table VI 0.2% Yield Ultimate Percent Percent Hard- Heat No Str. (p.s.i.) Str. (p.s.i.) Elonga- Red in ness tion Area Stress-rupture tests of several test members of each of the alloys of Example 'IV are indicated in Table VII:

Referring to Fig. 2 of the drawing, there are plotted curves derived from creep tests of Heat No. 1817 carried out under the conditions listed. These curves indicate the outstanding properties of the alloys of this invention.

In order to enable the user of the alloy to determine the stress to rupture as a function of the time-temperature parameter, the curve plotted in Fig. 3 of the drawing is highly helpful. The vertical ordinate plots stresses at the indicated loads. The horizontal ordinate is plotted from the following equation:

T is the temperature in degrees Rankin log t=logarithrn base of time in hours It will be noted that the 100-hour stress-rupture times at temperatures from 1500" F. to 2000 F. are indicated at the respective points A while the SOD-hour stress-to-rupture times are indicated by the points B for each of these respective temperatures. It will be noted that the various test results for five different heats of the alloy fall quite closely along the curve shown in Fig. 2.

The alloys of the present invention may be readily cast into turbine blades for gas turbines and jet engines, into bolts for high temperature apparatus, and into jaws and other fixtures employed in the high temperature zone of creep-rupture testing apparatus. Thus, precision cast blades from these alloys were produced by casting under an argon atmosphere and such blades had excellent surface finish. None of the known alloys possesses the combination of properties exhibited by the alloys of the present invention up to 1900 F.

Members of the alloys of the present invention will withstand the oxidizing action of air at temperatures of up to 2000 F. with very minor amounts of oxidation of the alloy for the useful life thereof. For instance, during stress-rupture tests at 1800 F. for periods of time of up to 800 hours in air, the specimens did not show any significant oxidation.

These alloys also possess an important property particularly desirable for many applications, namely, a high modulus of elasticity both at room temperature, an average of 35,000,000, and at temperatures of up to 2000 F. (for example, 24,000,000 at 1600 F.). These values were obtained by dynamic testing methods. As evidenced by these data, the rate of decrease of the modulus of elasticity with increase in temperature is comparatively small.

It will be understood that the above description and drawing are only illustrative of the invention.

I claim as my invention:

1. An alloy suitable for use at temperatures of up to 1900" F. consisting essentially of from 9% to 11% by weight of cobalt, from 9% to 15% by weight of chromium, from 6% to 10% by weight of tungsten, from 3.5% to 5.0% by weight of titanium, from 3% to 5% by weight of aluminum, from 0.04% to 0.2% carbon, from 0.02% to 0.2% boron, from 0.01% to 0.2% zirconium and the balance, at least 50% by Weight, being nickel except for incidental impurities and additions not exceeding 3% by weight, cast members of the alloys developing high creep strength properties without heat treatment.

2. The alloy of claim 1, wherein up to 2% iron, manganese up to 0.5% and silicon up to 0.5 are also present.

3. The alloy of claim 1, having less than 0.01% by weight of each oxygen and nitrogen, the alloy having been produced by melting under vacuum.

4. An alloy suitable for use at temperatures of up to 1900 F. at substantial stresses, consisting essentially of from 9.5% to 10.5% by weight of cobalt, from 11% to 13% by weight of chromium, from 7.5% to 8.5% by weight of tungsten, from 4.0% to 4.8% by weight of titanium, from 3.5 to 4.8% by weight of aluminum, from 0.08% to 0.13% by weight of carbon, less than 0.01% each of oxygen and nitrogen, from 0.02% to 0.08% by weight of zirconium, from 0.04% to 0.08% boron and the balance, at least 55% by weight, being nickel except for incidental impurities and additions not exceeding 3% by weight.

5. A cast member comprising an alloy suitable for use at a temperature of up to 1900 F. without heat treatment of the cast member consisting essentially of from 9% to 11% by weight of cobalt, from 9% to 15 by weight of chromium, from 6% to 10% by Weight of tungsten, from 3.5% to 5.0% by weight of titanium, from 3% to 5% by Weight of aluminum, from 0.04% to 0.2% carbon, from 0.02% to 0.2% boron, from 0.01% to 0.2% zirconium, and the balance, at least 50% by weight, being nickel except for incidental impurities and additions not exceed ing 3% by weight.

6. A cast member comprising an alloy suitable for use without heat treatment of the cast member at temperatures of up to 1900 F. at substantial stresses, consisting essentially of from 9.5% to 10.5% by weight of cobalt, from 11% to 13% by weight of chromium, from 7.5 to 8.5% by weight of tungsten, from 4.0% to 4.8% by weight of titanium, from 3.5% to 4.8% by weight of aluminum, from 0.08% to 0.13% by weight of carbon, less than 0.01% each of oxygen and nitrogen, from 0.02% to 0.08% by weight of zirconium, from 0.04% to 0.08% boron and the balance, at least 55% by weight, being nickel except for incidental impurities and additions not exceeding 3% by weight.

References Cited in the file of this patent UNITED STATES PATENTS 2,247,643 Rohn et a1 July 1, 1941 2,704,250 Payson Mar. 15, 1955 2,809,110 Darmara Oct. 8, 1957 FOREIGN PATENTS 710,413 Great Britain June 9, 1954 785,271 Great Britain Oct. 23, 1957 166,680 Australia Sept. 10, 1953 203,683 Australia Mar. 31, 1955 

1. AN ALLOY SUITABLE FOR USE AT TEMPERATURES OF UP TO 1900*F. CONSISTING ESSENTIALLY OF FROM 9% TO 11% BY WEIGHT OF COBALT, FROM 9% TO 15% BY WEIGHT OF CHROMIUM, FROM 6% TO 10% BY WEIGHT OF TUNGSTEN, FROM 3.5% TO 5.0% BY WEIGHT OF TITANIUM, FROM 3% TO 5% BY WEIGHT OF ALUMINUM, FROM 0.04% TO 0.2% CARBON, FROM 0.02% TO 0.2% BORON, FROM 0.01% TO 0.2% ZIRCONIUM AND THE BALANCE, AT LEAST 50% BY WEIGHT, BEING NICKEL EXCEPT FOR INCIDENTAL IMPURITIES AND ADDITIONS NOT EXCEEDING 3% BY WEIGHT, CAST MEMBERS OF THE ALLOYS DEVELOPING HIGH CREEP STRENGTH PROPERTIES WITHOUT HEAT TREATMENT. 